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REPORT 



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A SECTION OF THE RIVER DELAWARE, 



ONE MILE BELOW CHESTER, 



RICHMOND, ABOVE PHILADELPHIA. 



TAKEN 



BY ORDER OF THE COUNCILS. 



BY DJIVID M'CLURE. 



PUBIISHED BY OBDER OF COUNCIIS, 



PHILADELPHM.- 
PRINTED BY LYDIA R. BAILEY, 

JiTO. 10, NORTH STREET. 

1820. 



f"\SS 



REPORT 



THE SURVEY 



A SECTION OF THE RIVER DELAWARE. 



THE duty which the Councils of Philadelphia have 
assigned me, in the survey of a section of the river Dela- 
ware, I have completed ; and it is my consolation to know, 
and my privilege to assert, that I have not been faithless 
in the discharge of the important trust committed to me. 

As some accompanying remarks, with the draught of 
the survey, may be expected, I will endeavour to give 
them in as brief a detail as the nature of the case will 
admit. 

■■ To give a formal account, in this Report, of the methods 
adopted in the prosecution of the survey, is deemed unne- 
cessary ; and such information would only be interesting 
to professional men. A history, however, of the plans 
and methods pursued, has been laid before a few respect- 
able and professional gentlemen ; by whom the correctness 
thereof was duly investigated, and from whom those cer- 
tificates, which are respectfully submitted to the Councils 
at the close of this Report, were obtained. 

It may not be amiss, however, to state, that every at- 
tention was bestowed, to secure accuracy in the work, 
and to render the survey as full and as perfect as possible. 



A sloop and eight men were employed ; a liberal supply 
of the best mathematical instruments procured ; and the 
adoption of each plan, to suit the various cases in the 
survey, was determined with much deliberation. 

To secure accuracy in the work, no toils were spared. 
In many places, especially where there was splatterdock, 
water-grass, or soft mud, hardships and fatigues were 
endured of no common nature. All the islands, sand-bars, 
banks, whether natural or artificial, waterdock, commonly 
called splatterdock, and the mud, to the low-water mark, 
were faithfully taken. These various items are designated 
on the chart by appropriate colours and suitable explana- 
tions. 

The necessity of exhibiting the low water mark, water- 
dock edge, and banks, will at once be obvious, when we 
consider the very different aspects which the river exhi- 
bits in the different stages of the tide, particularly on long 
flats. The coves on the Jersey side, below Gloucester, 
and above Thompson's Point, present so different an ap- 
pearance at high and low water, that they would scarcely 
be taken for the same places. 

The banks always exhibit the high water mark ; and 
the edge of the mud or splatterdock, the low water mark. 

All the houses that are conspicuous from the water are 
also laid down, together with the wharves, wrecks of 
vessels, including the frigates Augusta and Marlin, and 
the buoys. 

The direction of the current when in its strength, toge- 
ther with its velocity, is marked in all those places where 
it was deemed most important. 

The compass exhibits the magnetic bearing of every 
two points. The true north, with the angle, containing 
the variation of the compass, two degrees forty-five mi- 
nutes west, obtained by an observation taken for the oc- 
casion, is marked in its proper place. 



The ship channel and sloop channels are marked with 
appropriate dotted lines. The depth of water is reduced, 
and exhibited as taken at low water. The nature of the 
bottom is carefully laid down, particularly where the 
places are important. Large beds of muscles were found 
in several places ; the most remarkable of which is that 
on the flats between Woodbury dam and Mantua creek, 
where they are so numerous that they seem to lie in con- 
tact with each other. 

The soundings taken on the shoals are numerous. The 
ordinary and general soundings are exhibited at short 
distances apart, and nearly at right angles across the 
river. 

The rise of the tide ahove low water was obtained by 
means of a machine invented for the occasion, and which 
was found admirably well calculated to answer the pur- 
pose. It consisted of an upright piece of wood, notched 
on each side like the teeth of a saw, into which a spring, 
made fast to a floating board, takes hold. The notches 
reversed, and boards appropriated to each, will accurately 
exhibit the high and low water mark. A more full de- 
scription is given in the Appendix. 

The plan of the survey was drawn by means of an in- 
vention which had been devised, not long previous, for 
such purposes. By this instrument, great accuracy and 
facility were attained in the draught. As this instrument 
may be of essential service to surveyors and others in 
plotting or draughting, it may be acceptable to such to 
have a description of the same, with the pri\'ilege of a 
free use thereof. (See Appendix.) 

Considerable changes have taken place in the river, 
since the last twelve or fifteen years. The island called 
Gibbet island, formerly opposite the mouth of Schuylkill, 
is entirely swept away : the fragments thereof seem to be 
scattered down the river, and to have formed a consider- 
able flat. 



6 

Bush island, formerly situated opposite Red Bank, has 
shared the same fate : the ground on which it stood, and 
for some distance below it, is considerably irregular and 
uneven. At both ends of Chester island, the flats seem 
to be increasing rapidly. 

It is remarkable, that where a narrow channel is found 
existing between an island and the main shore, the pas- 
sage which opens up the river is shoaling, while the depth 
of water increases down the channel. This is the case in 
the passage between Shivers' island and the Jerseys, be- 
tween Monnis island and the Jerseys, between Tinnicum 
island and Pennsylvania, between Hog Island and Penn- 
sylvania, between League island and Pennsylvania, be- 
tween Wind Mill island and the Jerseys, between Petty's 
island and the Jerseys. This circumstance seems imiver- 
sal, and consequently admits of a philosophical investiga- 
tion : it is deemed improper to enter upon it in this place. 

A caution naturally presents itself to those who may 
attempt passing through an inside channel from below, 
without a knowledge of the same. The depth of water 
which first presents itself may seem to intimate a channel 
of more than sufficient depth ,• and the unwary may be led 
on to a considerable distance, and almost to the upper end 
of the channel, before they find themselves entrapped by 
the shoal water. 

A considerable change has also taken place between 
Hog island and the Pennsylvania shore. Formerly, there 
existed a considerable channel in that place ; and it is well 
known, that during the revolutionary war a large British 
ship passed up that channel, and attacked the fort in the 
rear. At present, it can be forded at low water. The 
soldiers often desert, and ford this channel, a little below 
the fort, at low water. 

Between Maiden island, particularly towards the north 
end and the Pennsylvania side, a considerable change has 
taken place. 



That interesting part of our navigable waters, a little 
below fort Mifflin, and known by the name of the Bar, is 
subject to many changes. On taking the survey, it was 
found that the lower buoy was not situated in the most 
eligible place, owing to a change that had occurred dur- 
ing the preceding two or three months. The lower buoy 
is now removed considerably further up, so that the two 
buoys are very near each other. 

It was also found that a considerable shoal had formed 
between the north end of Tinnicum and the Pennsylvania 
shore, not exceeding two or three feet deep at low water, 
on which several small vessels grounded while we were 
surveying in that vicinity. A communication of the ex- 
istence of this shoal was immediately made, and a rough 
draft of the same forwarded to Joseph S. Lewis, Esq. chair- 
man of the committee appointed to superintend the survey, 
who reported the same to the proper authority. The buoys 
were accordingly directed to be placed in a proper posi- 
tion to designate the shoal, which has since been done. 

This channel should be navigated with great caution, 
on account of the irregularity of the ground, and the ra- 
pid cross current which prevails during the flood tide. 

The pier opposite fort Mifflin, formerly called Davis' 
pier, now known by the name of Gaines' fort, was sunk 
in the year 1777, in eighteen feet at low w^ater. To this 
pier is attributed the formation of a long bar, which ex- 
tends upwards of a mile down the river, and has proved 
very injurious to our navigation. 

The water seems to be undermining this pier very ra- 
pidly; and, unless something be speedily done, it will 
inevitably be thrown over into the river. In the year 
1813, under the direction of the master warden of this 
port, ten or twelve shallop loads of stone were thrown 
around this pier, for the purpose of preserving its safety, 
for which fears were then entertained. 



8 

At one of the corners towards the Jersey shore, there 
are now, at low water, twenty-eight feet ', which is neces- 
sarily from eight to ten feet below the foundation of the 
pier. The soundings around the pier are exhibited in the 
map. 

Between the upper end of League island and the Penn- 
sylvania shore, the bed of the channel is entirely exposed 
at low water. 

A considerable change has also taken place in the shoal 
or bar which exists at the north end of Wind Mill island. 
In the year 1777, a map was published by Mr. Scull, the 
then city surveyor, in which this bar is represented to 
be joined to the Jersey shore, at the point a little above 
Cooper's ferry. 

One proposition it is of importance to notice ; and that 
is, that wherever the water is impeded in its motion, and 
brought into a state of rest, or made to form what is call- 
ed an eddy or counter current, there the sediment will 
be deposited, and the place become shoal. This will be 
the case where wharves, piers, or wrecks, exist: or where 
a creek, sending its waters across the channel, checks the 
velocity of the ebb tide on the shore below it ; or where 
a creek, taking in the water on a flood, checks the velo- 
city of the flood tide above. Hence it is, that at the mouth 
of creeks we generally find flats. 

It is remarkable that the Jersey shore has almost all 
the flats. This may readily be accounted for, from the 
circumstance of the soil being more fragile and sandy, 
and less tenacious, than the Pennsylvania shore. 

Any obstruction in the river, has a tendency to change 
its direction ; and it is worthy of notice, that the current 
on the ebb is so directed by the piers below the fort, 
known by the name of the Boom piers, that it seems to 
take an oblique course immediately between the two buoys 
designating that part of the bar where the channel exists. 



It is probable, that if an improvement be made on these 
piers, by presenting an oblique side to the current, it 
may have the happy eiFect of throwing a larger quantity 
of water across the river, and thereby deepening the chan- 
nel on the bar. 

There is no doubt that the ebb tide gives the river its 
particular character and direction, since much more water 
passes down than up the river. It is on this account 
chiefly, that so great an inequality exists between the 
times of the ebbing and flowing of the tides ; the former 
being about seven, the latter only five hours. 

Bold banks are most exposed to the fury of a Adolent 
current ; while flats, especially when covered with grass, 
subdue the rage of a current almost into a calm. 

The winds have a tendency not only to give the current 
velocity, but also direction. Many artificial banks have 
been prostrated, by a strong wind directing the current 
against them. The banks of Hog island sometimes suffer 
much from the north-east gales. 

At the north-east end of this island, we found the pro- 
prietors engaged in making a new bank, in the rear of 
one which, in consequence of its being a little prominent, 
had frequently been almost prostrated before the north- 
east gales J and which was now deemed insufficient to stand 
those gales any longer. The old bank was surveyed, and 
the new one laid down. 

It would be an important improvement to these banks, 
to build them with a considerable declivity on the river 
side, so that the violence of the waves and current would 
thereby be much broken. 

At the upper end of Hog island, in consequence of the 
vast accumulation of ground recently made, the proprie- 
tors were erecting banks that will enclose at least fifty 
acres, and on the same place over which large sloops for- 
merly sailed, at high water. As these new banks Vt ere 



10 

jiearly completed, they were surveyed, and no attention 
paid to the old ones, as they will hereafter fall entirely 
within the boundaries of the island, and may perhaps 
soon be obliterated. 

The small shoal that exists between Tinnicum island 
and the Jersey shore, nearly opposite to Mr. Lodge's 
dwelling, was formed from a pilot boat which was sunk 
a number of years ago. 

The remains of the British frigate Augusta, whose his- 
tory is well known, lie at present in about six feet depth, 
at low water. The sand and mud have accumulated around 
her for some distance, and formed a considerable shoal, 
in which she is nearly buried. While we were surveying 
in the vicinity of that place, three or four eighteen pound- 
ers were grappled up from the wreck, by men whose sub- 
sistence depends on that business. The cannons are per- 
fectly free from rust, and are supposed to be in as good 
condition as they ever were, after having lain in the water 
upwards of forty years. 

More than ordinary attention was bestowed on that part 
of the survey which is immediately within the vicinity of 
the contemplated bridge. The direction of the current, its 
tendency to produce an effect, its velocity in ebbing and 
flowing, the depth and nature of the bottom, were taken 
with scrupulous exactness. The ebbing and flowing of 
the tides make first in this place, as is usually the case in 
the shoaler channels. 

The velocity of the current in this channel is much in- 
ferior to that of the western channel ; and, as a vertical 
section of the latter, in the narrowest place, is more than 
three times as great as the former, it must of necessity 
convey the great mass of water in the ebbing and flowing 
of the tides. 

The eastern channel has throughout a depth of twelve 
feet at low water, and in the narrowest part has a breadth 



11 

of four hundred and fifty feet, commanding a depth of ten 
feet at low water. 

This channel may be navigated, at high water, by our 
ships drawing fourteen feet. Our pilots are generally 
ignorant of the nature of this channel ; and on extraordi- 
nary occasions only would they be induced to prefer it, 
especially as it terminates above that part of the city 
where the shipping generally lies. 

Sloops often use this channel to an advantage | and, in 
contrary winds, and near high water, can tack more than 
three-fourths of the distance from shore to shore. A ves- 
sel coming up to Philadelphia, with the wind from the 
west, and the tide ebbing, may pass up this channel, and 
arrive at the city, when such arrival could not be effected 
by the western channel. Similar advantages are afforded 
to a vessel descending the river. 

Vessels bound above the city from below, may take tliis 
channel as the more direct course ; and, should there be 
an ebb tide, they will have less current to encounter than 
in the western channel. Vessels descending the river 
will have similar advantages. 

A strong westerly wind drives the great mass of ice 
into this channel, and relieves the western side. A con- 
trary wind produces a contrary effect. Each channel has 
been used by turns, as they have been thus cleared of ice. 

The water, on the ebb, coming out of Cooper's creek, 
throws the current over near the flats on the south end of 
Petty 's island, and has a direct tendency to check the water 
from flowing freely down this eastern channel. 

The ordinary rise of the tide is about five feet : but it 
is very variable, on many accounts. A strong easterly 
wind has been known to raise the tide three feet above 
the ordinary height | while a strong westerly wind has 
been known to depress it three feet below the ordinary 
low water. A long drought will sensibly depress the tide^ 
while heavy rains will not fail to raise it. 



12 

The moon also has her influence on the tides ; and the 
effect produced depends upon a combination of circum- 
stances. The highest elevation, and lowest depression, 
of tides, are produced, when, at the same juncture, there 
occur the time of the equinox, the moon in conjunction 
or opposition to the sun, and she near her perigee. A 
reverse position in the heavens will produce a reverse 
effect. 

The tide rises most rapidly on the first of the flood. In 
the short period of one hour and a half, the tide will be 
more than one half up. Annexed is a table, exhibiting 
the rise of the tide for every half hour, to the nearest 
inch, the fractional parts being rejected : 





The -whole rise 


The rise for 




of the tide. 


each half hour. 


ours. 


ft- 


in. 


ft- 


in. 


oi 


1 


2 


1 


2 


1 


2 


3 


1 


I 


H 


3 


2 





11 


2 


3 


11 





9 


H 


4 


7 





8 




5 


1 





6 


H 


5 


5 





4 


4 


5 


8 







4i 


5 


10 





2 


5 


5 


11 





1 



It is very remarkable that the tide rises in the ratio of 
ten inches for the first half hour, nine inches for the se- 
cond, eight inches for the third, and so on, in an arith- 
metical decrease, to unity. This simple ratio can be 
easily remembered, and from it the proportional rise of 
the tide may be readily calculated for any half hour, after 
the manner illustrated in the next page. 



13 

The following table exhibits the fall of the tide for 
every half hour^ to the nearest inch : 





The -whole fall 
of the tide. 


The fall for 
each half hour. 


hours. 


ft- 


«72. 


ft- 


in. 


oi 





8 





8 


1 


1 


4 





8 


li 


1 


11 





7 


2 


2 


6 





7 


2i 


3 








6 


3 


3 


6 





6 


^2 


3 


11 





5 


4 


4 


4 





5 


4* 


4 


8 





4 


5 


5 








4 


5| 


5 


3 





3 


6 


5 


6 





3 


6i 


5 


8 





2 


7 


5 


9 





1 



As the whole fall of the tide requires much longer time 
than the rise, it will necessarily be less rapid in falling 
than in rising. There appears, however, a considerable 
analogy in their ratios. The proportional fall of the tide 
for any half hour required, may be found by assuming 14 
for the first, 13 for the second, 12 for the third, and so on, 
in a decreasing arithmetical progression, to unity: for 
example, let it be required the proportional fall of the tide 
for one hour and a half, that is for three half hours ; 14, 
13, and 12, added, will be 39^ and the sum of 14, 13, and 
12, &c. to unity, is 105; therefore, as 39 is to 105, is the 
proportion required nearly one-third, which is agreeable 
to the table. 



14 

From the above table, it will be apparent, that the tide, 
in the short period of about two hours and one quarter, 
will be half down. 

The above observations were taken at a time when it 
was calm, and the tide about an ordinary height. A 
strong wind or freshet will necessarily affect the ratios 
of the rising and falling of the tide herein exhibited ; yet, 
notwithstanding, the proportions will nearly hold good 
in all cases. 

The effect of a freshet on the channel is twofold, — that- 
arising from an increased velocity of water, and from an 
increased quantity of sediment, which it invariably brings 
down. The effect of ice is most to be dreaded, when there 
are united with a freshet a high tide and strong winds. 

The tide originates in the ocean, and is principally 
the effect of the moon's attraction. The sun's attraction 
has a partial effect, producing a change on the principal 
effect. 

No motion is produced in the waters in the middle of 
the ocean, except a perpendicular one, equivalent to the 
rise of the tide. Were the globe a mass of water, there 
would be no horizontal motion occasioned by the tide. 

Some writers, and of reputation too, have however in- 
timated the contrary, and given us to understand, that 
the whole ocean, under the influence of the tide, has a 
horizontal motion. Dr. Young, in particular, mentions, 
that " the tide, entering the Atlantic, appears to advance 
northwards at the rate of five hundred miles an hour, 
corresponding to a depth of about three miles, so as to 
reach Sierra Leone at the eighth hour after the moon's 
southing." 

Dr. Young and others surely do not mean what they 
appear to intimate. We lament, to say the least of it, 
that their expressions are unfortunate, and too much cal- 
culated to lead inquiring minds astray. 



15 

The horizontal motion of the sea, near the land, and 
up hays and rivers, is not the immediate and primary ef^ 
feet of the moon or sun's influence ^ hut arises from the 
circumstance, that the abutments (to use a figure) of the 
great arch of the elevated water being too weak near the 
shore, by reason of shoalness, to sustain the pressure, a 
horizontal motion is produced, the eifect of which is felt 
at great distances, up channels, bays, and rivers. 

The momentum which the waters thus receive, is not 
an absolute motion of the whole mass of watery but some- 
thing like the impulses of the air, or like that motion 
which is produced on throwing a stone in the water. 

The high water at Cape May is about six hours reach- 
ing Philadelphia, a distance of about a hundred and twenty 
miles. Now, if this tide be the effect of an absolute hori- 
zontal motion of the whole mass of water, then the tide 
must move at the rate of twenty miles per hour, which far 
exceeds the true velocity. It is near low water at Phila- 
delphia, when it is high water at Cape May,- and vice 
versa. 

The tide has been very justly compared to a wave, the 
top of which is at the Cape, and the bottom near Phila- 
delphia. A vessel leaving Cape May in the early flood, 
and arriving in Philadelphia within eleven hours, will 
bring the flood tide the whole distance with her. But, in 
descending the river, the tide will be anticipated one hour 
in about the distance of every twenty miles. 

The momentum, as explained above, which the tide has 
on entering a river, is the whole body of water multiplied 
into its celerity ; and if this momentum be not powerfully 
diminished by friction, it will have a tendency to press 
with considerable force as the river narrows and shoals, 
thereby making up in velocity what it loses in space; the 
effect of which will be, that the water will have sufficient 
power to ascend the river considerably above its natural 
level. 



16 

If Philadelphia be supposed to be a hundred feet above 
the level of Cape May, the angle of ascent will in that 
case not exceed half a minute of a degree, which very 
gradual declivity the tide would not require much force 
to surmount. We can scarcely suppose that the high water 
mark at Philadelphia, so many miles from the ocean, is 
not above the level of the high water mark at Cape May. 
Were fifteen or twenty miles faithfully levelled, it would 
fully establish the truth. 

The more irregular the river is, and the more shoals 
and islands in it, the greater will be the friction, and 
consequently the less will be the force of the water to 
ascend above the level. 

If a trough be made, and placed in a position a little 
elevated, with the one end in water, it will be found, on 
producing a wave, that the water will ascend in the trough, 
and rise considerably above its level, especially if the 
sides of the trough be converging to each other from the 
water. 

It is probable that a declivity of the river is an addi- 
tional cause to that already stated, for the inequality in 
the times of the ebbing and flowing of the tides. 

A log, set afloat in the middle of the current, on the 
first of the ebb, will never return on the flood to the same 
place, unless it descend twenty miles, and have a current 
equally strong on the flood. If the log descend twenty 
miles, it will anticipate the flood one hour, and conse- 
quently will only have six hours in descending ; and if 
the current be equally strong on the flood, the log in re- 
turning will gain one hour, whicli will make its whole 
time on the flood six hours, equal to the time on the ebb, 
and therefore it will be brought precisely back to the 
place whence it started. 

If the log descend more than twenty miles, it will, on 
the flood, I'eturn and pass above the place left. For 
example, if we suppose it to descend forty miles below 



17 

Philadelphia, it will anticipate the flood two hours, and 
therefore will only he five hours in descending ; and the 
flood, having the same velocity, will hring it back in five 
hours, and gain on the flood two hours ; in which time, 
at the same rate, it will ascend sixteen miles above Phila- 
delphia, from which place it was supposed to start on the 
first of the ebb. 

It seems a paradox to say, that the farther down the 
river the log descends on the ebb, the farther up the river 
it will ascend on the flood : but the fact has been made 
very obvious. 

AVe cannot, however, reverse the proposition, and say, 
that the least distance the log will descend on the ebb, the 
farther it will be below the place on the close of the flood. 
There must therefore be a point, to which, if the log de- 
scend, it will, on the close of the flood, be the farthest 
distance possible below the place left, supposing, as be- 
fore, the strength of the ebb and flood tides to be equal. 

To ascertain this point, the following solution is pro- 
posed,' and, by its plainness, is accommodated to those 
who may not be much versed in the mathematics : 

n = number of minutes difference of tide in 1 mile, = 

3 minutes. 
a = number of minutes the tide ebbs. 
6 = number of minutes the tide flows. 
X = distance carried down by the ebb. 
a — n X = time in descending with the ebb. 
1/ = the distance brought up on the flood. 

X : (h—nx : : ij : a y—n x y ^ rthe time coming 

X Xup on the flood. 

Again, b+n y= also the time coming up on the flood. 

Therefore, a y — n x y 



X 

And y =bx 

-2 nx 



b+ny 



iS 



b X 
Consequently, x is a maximum. 

a — 2 11 X 



The fluxion of which is x — h ax 



a — 2 11 X I 



2 



fl2 X — 4 a % a? as'+4 -/i^ a:^ a? — & ax= 
4 w^ x^ — 4 anx = b a — a^ 
x^ — a X b a — d^ 



11 4 ir 



X^ — a X a^ b a 

— I 

I ^ 4i 

a + 1 



H = 

11 4 11^ 4 11^ 



X == 



= — — -r— ^-j— =10.838966, the distance sought. 

So that the distance sought will he 10 miles 14r6 yards, 
and will be 6h. 27' 29" in descending. The log on the 
flood will return 9 miles 281 yards in 5h. 27' 29", which 
is 1 mile 1195 yards below the place left, the greatest 
distance possible, supposing both tides of equal strength. 

The tide falls considerably towards the close of the 
flood, and before the current begins to run down in the 
middle of the river. It was found, on repeated trials, to 
vary from six to twelve inches in its fall, and to be from 
thirty minutes to one hour and a half in falling. The wind 
from the southward prolongs the time of its falling, and 
produces the greatest fall ; but the wind from the north- 
ward produces the contrary effect. 

This circumstance induced a suspicion, that the water 
towards the bottom of the river descended, while it was 
running up on the top. Not that the sinking must neces- 
sarily depend on the water descending tlie river ; for the 
tide, like a wave, may continue to run up, and rise, until 
its apex has passed, and then produce a consequent sink- 
ing, without a particle of water descending the river. 



19 

However, to ascertain the truth, a long cylindrical 
piece of wood was procured, and loaded at one end, by 
putting lead into a cavity formed for the purpose, until it 
was made to sink in a perpendicular position, so as to 
leave only about three feet out of water. 

Now it is evident, that if this pole be placed in the cur- 
rent, it will show, by its inclination, whether the top or 
bottom of the river has the greater velocity ; for, if the 
rod incline forward, according to the direction of the cur- 
rent, it is an evidence that the water towards the surface 
has the greatest velocity ; but if it incline backward, it 
shows that the swiftest current is towards the bottom : if 
it retain a perpendicular position, the current in that case 
must either have an equal velocity from the top to the 
bottom, or have the least one near the middle, while to- 
wards the surface and bottom the velocities must either 
be equal, or so adjusted by different celerities, as to keep 
the pole in that position. 

In this way, several trials were made; and it was 
found, that both on the ebb and flood tide, the pole in- 
clined at the top up the river, indicating thereby that the 
bottom had the greater velocity on the ebb, and the top 
the greater on the flood. On the ebb, the pole, as an 
evidence of this, moved faster than the boat which was 
left to float down after it, but on the flood it was found to 
move slower. 

It was truly remarkable, that, near the close of the 
flood tide, the pole first became stationary, and shortly 
afterwards began to descend the river, while on the sur- 
face every thing was drifting up. These facts fully esta- 
blished the point which first induced the experiment to be 
made. 

To make a more complete investigation of the different 
velocities of the river, from the surface to the bottom, the 
following plan was pursued. A large boat was procured, 
and anchoi'ed in the njiddle of the river, nearly opposite 



20 

Walnut street ; at the stern of which was fixed the trian- 
gular instrument ABC, (See Fig. 1.) whose sides were 
about four feet in length. The side B C was graduated in 
degrees and quarters, about A as a centre, and numbered 
from B to C. Through the centre A, a bolt was fixed, 
by which the instrument was suspended, and over which 
a line, fastened to a nine pound ball, W, was passed. To 
this bolt also was suspended the weight R, by which the 
side A B was brought into a perpendicular position, when 
in use. The line to which the weight W was fastened, 
was marked by loops, tied at every five feet apart. 

Thus prepared, the velocity of the tide was taken on 
the surface, in the usual way, for every fifteen minutes, 
during the whole of the flood and ebb ; and also the an- 
gles, which the string A W made with the perpendicular 
line A R, taken from the graduated side B C, at the ob- 
lique distance of every five feet from the surface of the 
water to the bottom. 

From these oblique distances and angles, the perpendi- 
cular depths were calculated ; and from this depth the 
corresponding angles were proportioned for every five 
feet. To illustrate which, the following is an example : 



5 


10 


15 


20 


25 


30 


35 


40 


45 


50 


55 


60 


65 


8 


12 


16 


20 


23 


26 


29 


31 


33 


34 


35 


36 


37 


5 


9.8 


14.4 


18.8 


23 


27 


30.6 


34.3 


37.7 


41.5 


45.1 


48.5 


51.9 


8. 


12 


16 


21 


25 


28 


31 


34 


35 


36 









The first line exhibits the oblique depths of every five 
feet ; the second, the angles which were found to corres- 
pond to the same; the third, the perpendicular depth, cal- 
culated for each angle and oblique depth ; and the fourth 
is the angle under which the line A W will make with the 
perpendicular line A R, corresponding to the nearest de- 
gree, proportioned for every five feet perpendicular depth. 
For example: to the perpendicular depth of 18.8 feet, the 
corresponding degree is 20, and to 23 feet 23 degrees 5 



21 



therefore, 21 is the nearest proportional degree for a^er- 
pendicular depth of 20 feet. 

The following table is the result of an experiment on 
the flood tide, taken on the 8th June, 1820, two days be- 
fore the new moon. The first column shows the times at 
which the observations were made ; the second, the velo- 
city of the current at those times, exhibiting its rate per 
hour, in statute miles and hundredths ; the remaining co- 
lumns, the different angles, corresponding to every five 
feet perpendicular depth, marked on the top : 



Time 


Bate of 
current. 


5 


10 


15 


20 


25 


30 


35 


40 


45 


50 


8 


Slack 






water. 






















8i 


0.25 


1 


2 


3 


4 


5 


6 


7 


7 


8 


8 


H 


0.75 


3 


5 


8 


11 


13 


15 


17 


19 


20 


21 


8| 


1.15 


5 


8 


11 


14 


18 


23 


28 


29 


29 


29 


9 


1.87 


9 


14 


20 


27 


33 


37 


41 


44 


46 


48 


H 


2.17 


11 


16 


22 


29 


37 


45 


50 


54 


56 


57 


9| 


2.20 


12 


17 


23 


30 


38 


45 


50 


55 


57 


58 


91 


2.23 


12 


19 


27 


35 


42 


48 


51 


55 


57 


58 


10 


2.32 


12 


20 


29 


37 


45 


52 


56 


59 


61 


61 


lOi 


2.40 


13 


20 


28 


36 


44 


51 


54 


57 


59 


59 


lOi 


2.40 


13 


20 


28 


36 


44 


51 


54 


57 


59 


59 


10| 


2.37 


13 


20 


28 


36 


44 


50 


53 


56 


57 


57 


11 


2.37 


13 


20 


28 


36 


44 


49 


51 


53 


55 


55 


Ui 


2.27 


12 


17 


23 


29 


37 


45 


50 


52 


54 


54 


Hi 


2.25 


10 


15 


21 


27 


33 


38 


41 


43 


45 


45 


111 


1.78 


8 


12 


16 


21 


25 


28 


31 


34 


35 


36 


12 


1.60 


6 


9 


12 


15 


17 


20 


23 


25 


26 


27 


12i 


1.15 


3 


5 


7 


9 


10 


11 


12 


13 


14 


14 


12§ 


0.75 


1 


2 


2 


2 


3 


3 


3 


4 


4 


4 


12| 


0.32 
































1 


Slack 
water. 








1 


1 


2 


2 


3 


3 


4 


5 



At 1 o'clock, it was slack water; at which time, the angles were 
made down the river. 



22 



The following was taken on the ebb tide, the same day : 



Time. 


current. 


5 


10 


15 


20 


25 


30 


35 


40 


45 
9 


50 
10 


H 


0.42 


1 


2 


3 


4 


5 


6 


7 


8 


H 


1.12 


3 


5 


7 


9 


11 


13 


15 


17 


19 


21 


If 


1.50 


6 


9 


12 


15 


19 


23 


27 


31 


34 


37 


2 


1.60 


7 


11 


15 


20 


25 


31 


37 


42 


46 


48 


H 


2.0O 


10 


16 


23 


30 


38 


45 


48 


50 


52 


53 


n 


2.32 


12 


20 


29 


39 


49 


57 


62 


64 


65 


66 


n 


2.37 


12 


20 


29 


39 


49 


57 


62 


64 


65 


66 


3 


2.25 


13 


21 


30 


40 


51 


58 


63 


65 


67 


68 


H 


2.25 


13 


21 


30 


40 


51 


58 


63 


65 


67 


68 


H 


2.25 


13 


21 


30 


40 


51 


58 


63 


65 


67 


68 


3| 


2.37 


14 


22 


31 


41 


51 


58 


63 


65 


67 


68 


4 


2.32 


13 


22 


31 


40 


49 


56 


60 


62 


64 


65 


4i 


2.30 


13 


22 


31 


40 


48 


54 


57 


59 


61 


62 


H 


2.30 


13 


22 


31 


40 


48 


54 


57 


59 


60 


61 


4| 


2.26 


13 


22 


31 


39 


47 


52 


56 


58 


59 


60 


5 


2.25 


13 


21 


30 


38 


45 


49 


54 


57 


58 


59 


H 


2.25 


12 


20 


29 


37 


45 


49 


53 


55 


57 


58 


sh 


2.25 


12 


20 


29 


37 


45 


49 


53 


55 


56 


57 


51 


2.00 


12 


20 


29 


37 


45 


49 


53 


55 


56 


57 


6 


2.00 


11 


19 


27 


36 


45 


49 


52 


53 


54 


55 


6* 


2.00 


11 


18 


27 


36 


45 


49 


52 


53 


54 


55 


6^ 


2.00 


10 


17 


26 


35 


45 


49 


51 


53 


54 


55 


6| 


2.00 


10 


16 


24 


32 


40 


47 


49 


50 


51 


51 


7 


1.75 


8 


14 


20 


25 


28 


31 


36 


38 


41 


43 


7"* 


1.00 


4 


6 


8 


9 


10 


11 


11 


12 


12 


13 


74 


0.27 








1 


1 


1 


2 


2 


2 


3 


3 


7 35' 


Slack 
water. 
































7# 


0.50 


2 


3 


4 


5 


6 


6 


7 


7 


8 


8 



At 7 o'clock and 45 minutes, it was flood tide. 

From these tables, tlie velocity of the water may be 
calculated for the depth of every five feet, on the princi- 
ples of the inclined plane, in which we have the size and 
density of the ball, and the angle under which it was kept 
in equilibrio. The rope by which the ball was suspended 
was one-sixth of an inch in diameter, for which an allow- 
ance must be made. These tables will be found of essen- 
tial service, in pursuing various investigations that may 
be made on the tides. 



23 

Another method, to obtain the different velocities of the 
current, was devised, equally accurate, while, at the same 
time, it was simple, and less incumbered with calculations. 
It nearly agrees with the calculations resulting from the 
first experiment. 

Let A (Fig. 2.) represent the stern of the large boat, 
which was anchored near the same place where the first 
experiment was madej B, a board about four feet in length, 
sharpened at both ends; A B, the log line, fastened to the 
end of the board, by which the different velocities of the 
tide were obtained ; D, a nine pound ball, immediately 
over which was fixed a cross-square to hold the water, 
the pieces of which were made of thin stuff, about one foot 
long and four inches broad, and the upper edges bevelled, 
so as to lessen the resistance while drawing it in. The 
line C D, by which tlie ball was suspended, had loops 
fastened at every ten feet, so that, by means of a hole in 
the middle of the board B C, and a stick to pass through 
those loops and rest on the board, the ball was readily 
suspended at every ten feet from the surface of the w^ater 
to the bottom. 

A loop was also fixed immediately over the cross-square, 
so that the ball, when suspended by it, was not more than 
eight or ten inches under water. In this last position, 
the rate of the surface of the water was taken ; and, by 
lowering the ball from one loop to another, the velocity of 
the current was obtained for the depth of every ten feet. 
An allowance must be made for the resistance of the board, 
and of the rope, which was one-sixth of an inch in dia- 
meter. 

It is evident, that when the velocity exhibited in the ta- 
bles, at any depth, is greater than that on the surface, 
the true velocity will be something more. But when less, 
the true velocity will be less. As the ball and cross-square 
present a large proportion of resisting surface, the true 
velocities cannot differ much from the tables. 



24 

The following table is the result of an experiment, 
taken on the 1st of July, 1820, one day before the last 
quarter of the moon, and on the ebb tide, for every half 
hour. The first column shows the time ; the second, the 
rate on the surface ; and the remaining columns, the rate 
for every ten feet depth, all of which are given in statute 
miles and hundredths : 



Time. 


Rate of 
current. 


10 


20 


30 


40 


50 


6| 


Slack 












water. 












7i 


0.60 


0.80 


1.00 


1.05 


1.20 


1.20 


7i 


1.25 


1.50 


1.75 


1.85 


1.95 


1.95 


8i 


2.12 


2.25 


2.40 


2.50 


2.40 


2.30 


8| 


2.65 


2.50 


2.40 


2.30 


2.40 


2.45 


H 


2.50 


2.48 


2.46 


2.45 


2.45 


2.45 ' 


9| 


2.62 


2.55 


2.50 


2.45 


2.35 


2.30 


lOi 


2.40 


2.40 


2.42 


2.42 


2.35 


2.30 


lOf 


2.25 


2.35 


2.45 


2.40 


2.36 


2.32 


Hi 


2.25 


2.40 


2.52 


2.39 


2.28 


2.15 


111 


2.12 


2.20 


2.36 


2.34 


2.31 


2.25 


I2i 


2.12 


2.14 


2.15 


2.17 


2.09 


2.08 


121 


2.00 


2.15 


2.18 


2.20 


2.14 


2.09 


H 


1.87 


1.87 


1.90 


2.00 


1.82 


1.75 


2 


0.85 


0.88 


0.92 


1.05 


0.83 


0.78 


Slack 












water. 













On inspecting the above table, it will be found, that, at 
6 o'clock and 45 minutes, it was slack water on the sur- 
face, at which time the velocities for the different depths 
were not taken. At the second hour, the tide has the 
greatest velocity; and, after diminishing its velocity, 
during the third hour, it again increases for a short time. 
This occurred in both experiments, which may be seen 
on comparing the tables. 

At 71, 7|, and 8|, the velocity towards the bottom was 
the greatest ; at 8|, 9^, and 9|, the velocity towards the 
top was the greatest j and during the remaining times, 
the middle of the liver had the greatest velocity. It has 



25 

been observed, that the top of the pole, on the few trials 
that were made on the ebb, uniformly pointed up the 
river. It will be found, on inspecting the table, that a 
pole about thirty feet long will always retain that posi- 
tion, except about one hour and a half from the second 
hour of the ebb, about which time a trial with the pole 
had been omitted. 

The following was taken on the flood, the same day : 



Time 


Rate of 
current 


10 


20 


30 


40 


50 


n 


1.43 


1.40 


1.35 


1.28 


1.25 


1.25 


3 


2.89 


2.86 


2.80 


2.75 


2.70 


2.70 


3g 


2.87 


3.00 


2.82 


2.76 


2.62 


2.60 


4 


3.00 


2.95 


2.85 


2.85 


2.85 


2.80 


4i 


3.00 


2.85 


2.82 


2.80 


2.76 


2.75 


5 


2.75 


2.68 


2.50 


2.48 


2.42 


2.40 


5§ 


2.37 


2.29 


2.27 


2.25 


2.20 


2.20 


6 


1.77 


1.90 


1.95 


1.72 


1.67 


1.60 


6i 


1.50 


1.40 


1.35 


1.32 


1.28 


1.25 


6| 


1.00 


0.85 


0.80 


0.78 


0.75 


0.55 


7 


0.75 


0.62 


0.35 


0.12 


Stat'y 


Des'g-. 
0.15 


H 


Slack 
water 


0.10 


0.23 


0.28 


0.35 


0.37 



On inspecting the above table, it will be found, that 
at the second hour, the tide has its greatest velocity, 
and that almost uniformly the surface of the water has 
the greatest velocity. Towards the close of the flood, 
the velocities were taken for every quarter of an hour, 
as it was then important to ascertain minutely every 
change. 

At 7 o'clock, at the depth of forty feet, the board was 
stationary ; and, at the depth of fifty feet, the tide was 
descending the river. At 71, it was slack on the top, 
while the board descended the river, with the different 
velocities annexed to the different depths. 

4 



26 

It is probable that the tide begins to run down at the 
bottom at least half an hour before the top. At 7 o'clock, 
at the depth of fifty feet, the board was drawn down the 
river, when at the same time the top had the velocity of 
three quarters of a mile per hour up the river: from which 
it will be evident, that the current towards the bottom, at 
that time, must have had a considerable velocity, such as 
to communicate to the ball and cross-square a sufficient 
force to overcome the resistance near the surface. 

The velocity with which the board left the boat, for 
the first twenty or thirty feet after the ball had been 
lowered forty or fifty feet, was ve^'y remarkable. As 
nearly as could be estimated, it moved at the rate of 
from fifteen to twenty miles per hour. A considerable 
length of stray line (as it is termed) was allowed the 
board, so that it should have full time to acquire the 
proper and uniform velocity of the current. From these 
experiments, many results, of practical importance, may 
be deduced. It is apparent, from the table, that a small 
vessel will drift faster on the flood than a large one, and 
slower on the ebb. 

From the first experiment, it appears, that the velocity 
of the whole ebb was sufficient to have drifted the dis- 
tance of 12.47 miles, supposing no anticipation of the 
tide down the river, and on the flood 8.15 miles, which 
makes the distance on the ebb in a greater proportion 
to the flood than their periods of ebbing and flowing, 
seven and five hours. In the second experiment, the 
reverse of this is found to be the case. This difference 
arises either from the irregularity of the sun and moon's 
influence, or from the effects of wind or freshets, whicli 
increase the velocity, and prolong the ebb tides. How- 
ever, in forming an estimate, we have reason to con- 
clude tliat their mean velocities will be about equal, and 
their distances in proportion to their times of ebbing 



. 2T 

and flowing, agreeably to the supposition made in the 
solution of the proposition respecting tlie descent of the 
log. 

From this proposition, and the velocities of the tides 
thus considered, it may be inferred that the whole of the 
upper water brought down the river during twelve hours, 
would be sufficient to fill a space included in a section of 
the river 1 mile 1195 yards in length. 

The contents of this space may be found, by taking 
the sum of all the soundings exhibited in the draught, 
in one line across the river, and dividing the same by 
the number of soundings, for the mean depth : this being- 
multiplied by the breadth of the river, will give the area 
of a vertical section in that place. A number of these 
sections near Philadelphia were calculated, and the mean 
was found to contain 51,000 superficial feet, which, mul- 
tiplied by 1 mile 1195 yards, or, which is nearly equal 
to the same, by 9,000 feet, will give 459,000,000, the 
contents of the space required, in solid feet. Each solid 
foot contains about 7i gallons, from which the contents 
are found to be 3,442,000,000 gallons, equal to 54,000,000 
hogsheads. 

The greatest velocity of the current is generally about 
the deepest part of the river. In shoal water, it is greatly 
diminished by the friction of the bottom, particularly 
when it is rough and uneven. 

Those places have an increased velocity on the ebb, 
where t!ie vertical sections are less than those farther 
up the river; but where the vertical sections are greater, 
there will be a diminution of velocity, except there be a 
creek or river some short distance above, whose waters 
will sufiice to fill the proportional increase of that sec- 
tion. 



28 

The following list exhibits some of the most important 
sections in the survey : — 

feet. 

From Richmond to Petty's island, 2,550 feet, 

mean depth 14 feet, area of section - 35,700 

In the same line from Petty's island to Jersey, 
1,500 feet, mean depth 14.3 feet, area of 
section - - - - 21,450 



Whole area, from Richmond to Jersey, - 57,150 

From Pennsylvania to Jersey, crossing to the 
south of Petty's island, 4,500 feet, mean depth 
12.5 feet, area of section - - 56,250 

From Cooper's Point to Nagle's vi^harf, at the 
mouth of Cohocksink creek, 3,000 feet, mean 
depth 20 feet, area of section - - 60,000 

In the eastern channel, the smallest section is 
from a point a little above Cooper's ferry to 
the bar, 1,300 feet, mean depth 7 feet, area 
of section - - - - 9,100 

From Walnut street wharf to the island, 900 

feet, mean depth 30.5 feet, area of section - 27,450 

In the same line from the island to Jersey, 2,100 

feet, mean depth 9 feet, area of section - 18,900 



Whole area, from Walnut street to Jersey, - 46,350 

The section in the eastern channel, from the 
south end of the island to Jersey, 1,680 feet, 
mean depth 13.3 feet, area of section - 22,344 

From the Pennsylvania to the Jersey shore, 
about half a mile below Kaign's Point, 3,300 
feet, mean depth 15.2 feet, area of section - 50,160 

From the wharf at Greenwich Point to Jersey, 
2,250 feet, mean depth 21 feet, area of sec- 
tion - - . . . 47,250 



29 



feet. 



From a point about half a mile below the wind- 
mill, in the Cove, to League island, 4,500 
feet, mean depth 17.5 feet, area of section - 78,750 

From the south end of League island to Jersey, 
4,200 feet, mean depth 14.8 feet, area of sec- 
tion - . - . . 62,160 

From Fort Mifflin to Jersey, 5,100 feet, mean 

depth 13.8 feet, area of section - - 70,380 

From Mud island, across the channel on the 
bar, to Jersey, 4,800 feet, mean depth 15.8 
feet, area of section - _ - 75,840 

From the Jersey to the Pennsylvania shore, in 
a line with the north end of Maiden island, 
4,800 feet, mean depth 14.4 feet, area of sec- 
tion . . - . - 69,120 

From the Jersey to the Pennsylvania shore, in 
a line with the south end of Tinnicum island, 
5,700 feet, mean depth 16.4 feet, area of sec- 
tion - _ - _ . 93,480 

From Chester to Jersey, 6,600 feet, mean depth 

17.6 feet, area of section - - 116,160 

From the north end of Schiver's island to the 
Pennsylvania shore, 5,400 feet, mean depth 
24.6 feet, area of section - - 132,840 

From the nortli end of Schiver's island to .Jer- 
sey, 1,500 feet, mean depth 4 feet, area of 
section . - - - > 6^000 



Area of whole section, from the Jersey to the 

Pennsylvania shore, - - - 138,840 

The narrowest part of the river, between Windmill 
island and Pennsylvania, is the line drawn at right an- 
gles to Smith's wharf on the island. The section across 



30 

from Walnut street will be nearly the smallest in this part 
of the river J but in the eastern channel, the smallest sec- 
tion is a little above Cooper's ferry to the bar, which is 
less than a third of the smallest section in the western 
channel, as has been stated in a former part of the Report. 
The section in the eastern channel, opposite Walnut street, 
is more than double the smallest section in that channel. 

From a view of the foregoing list of sections, it is evi- 
dent that at Walnut street, and at Greenwich Point, the 
velocity of the current must be greatly increased ,* and in 
the Cove below Gloucester and the Windmill, much de- 
creased. The water flowing out of Timber creek is much 
less than the proportional increase of that section. 

The sections, upon the whole, are gradually increasing 
down the river. The last section in the list contains np- 
wards of double the area of the first. Their distance 
apart is about twenty -tbree miles. In this distance, there 
are a number of creeks entering the river ; to accommo- 
date the waters of which, an increase in the bed of the 
river is necessary ; otlierwise, a considerable increase in 
the velocity of the current would be the result. 

On the Pennsylvania side, are Cohocksink and Hol- 
lander's creeks, Schuylkill river, Derby, Crum, Ridley, 
and Chester, creeks. On the Jersey side, are Cooper's, 
Newton, Timber, Manto, Clemell, and Popo, creeks. 
These afford a much greater body of water to the Dela- 
ware, than is afforded at any other part of the river within 
the same distance. 

The changes that take place in the river are a subject 
of primary importance. To it, attention has been direct- 
ed, from first to last. It is obvious, that these changes 
are effected by the water, either directly or indirectly, 
nnder the influence of its velocity and direction. 

On this subject, much has been written ; and it is hum- 
bly conceived that important materials are here afforded, 
for the further investigation and improvement of this 



31 

much-neglected, though important, branch of natural phi- 
losophy. It is true, that all that can be expected is to 
establish general principles. To pretend to bring this 
subject to so great a perfection as to be able to anticipate 
precisely all the changes that will take place, would be- 
tray as much presumption and ignorance as is displayed 
in our almanacs, where we are informed of the state of 
the weather for many months to come. 

It is possible, that the freshet of one day may be pro- 
ducing and carrying on certain eiFects, which a strong 
wind, or body of ice, may, in a few days afterward, avert, 
and produce a contrary impression. 

Taking into consideration, therefore, the constant 
changes of the winds, of the rise of tides, of the uncer- 
tainty of freshets, of ice, and of local obstructions which 
are sometimes thrown in the channel, it would be impos- 
sible to foretel precisely what changes may take place. 
It is well known that variations have occurred, very con- 
trary to the expectations of judicious persons. 

Yet, notwithstanding the subject will admit of much 
profitable investigation, and although we may not be led 
fully to anticipate what changes may hereafter occur, yet 
we may advance so far in improvement, as to be able to 
calculate, with some degree of certainty, what would take 
place under certain circumstances. 

Such land-marks were preserved, in the survey, as were 
likely to prove serviceable in ascertaining the changes 
that may result in the course of time. It would be highly 
advisable, that, every few years, the changes, at least for 
the most important parts of the river, be ascertained and 
reported. Such inspection would not be attended with 
much expense, and would be highly profitable. 

Thus I have rapidly glanced over such subjects as ap- 
peared to have a direct claim to my attention, in the sur- 
vey of the river. Much more might be added, particu- 



32 

larly in such speculatiA^e inquiries as might have a prac- 
tical bearing on the improvement of our navigable waters. 
This, however, is reserved for more mature deliberation. 

I cannot close this subject, without expressing the 
various sensations experienced on meeting the remains 
of those ships of war, some of which had been employed 
by our enemies, during our ever memorable revolution, in 
opposing our liberty and independence ; while others were 
employed by our worthy forefathers, and made the ho- 
noured instruments by which they asserted our rights, 
and freed us from bondage. 

Here lie the Augusta and Marlin, perishing in our 
waters in disgrace, their memory only retained as tro- 
phies of victory. There lies the memorable frigate Alli- 
ance : she maintained her post, in the struggle for free- 
dom, when all the rest of our ships were swallowed up in 
the contest. Her decks once bore the bold, intrepid Paul 
Jones, under whose command she often rode victorious. 
Worn out in service, her remains now repose near the 
\vestern banks of Petty 's island, now the soil of liberty 
and freedom. Nor shall she lie forgotten, while the vic- 
tories won are worth the recollection, or this pen lives to 
record her memory. 

DAVID M'CLURE. 

July 4, 1820. 



APPENDIX. 



THE following is a list of the soundings, in feet, at 
low water, at some of the most important parts of the 
river, taken at right angles across from shore to shore. 
They are obtained from the map, at certain equal dis- 
tances apart ; so that the relative situation of each depth 
is readily found, by dividing a line into one part more 
than the number of soundings, and annexing to each 
point of division the depth in the order exhibited in each 
line. 

From Richmond to Petty 's island, 10, 15, 10, 9, 18, 19, 
20, 21, 20, 15, 11, 14, 12. 

In the direction of Richmond, from Petty's island to 
Jersey, 12, 16, 20, 24, 22, 14, "S. 

From the east point of Petty's island to Jersey, 19, 38, 
23, 16, 18, 10. 

Across the mouth of Cooper's creek, from west to east, 
1, 3, 5, 8, 5. 

From the wharf at the Glass-House to Petty's island, 
16, 28, 33, 32, 25, 22, 21, 14. 

From the south point of Petty's island to Pennsylvania, 

4, 12, 18, 25, 34, 38, 26, 12, 3. 

From the south point of Petty's island to Jersey, 1, 3, 

5, r, 20, 22, 21, 18, 15, 12, 11, 8, 10. 

From Nagle's wliarf, at the moutli of Cohocksink 
creek, to Cooper's Point, 29, 40, 34, 26, 20, 18, 18, 16, 
16, 18, 19, 19, 13, 14, 11. 

5 



34 

In the direction of Callowhill street, from Pennsylvania 
to Jersey, 37, 46, 44, 33, 22, 17, 11, 6, 4— bar — 2, 8^ 
10, 12, 10, 6, 5. 

In the direction of High street, from Pennsylvania to 
Jersey, 42, 42, 37, 28, 10, 2, 1^— bar— U, 2, 5, 7, 11, 
12, 12, 11, 7, 7, 7, 4. 

In the direction of Walnut street, from Windmill island 
to Jersey, 2, 5, 9, 11, 12, 12, 12, 9, 8, 10, 9. 

From the first wharf above Pine street to the wharf on 
Windmill island, 43, 44, 39, 29, 18. 

From the south end of Windmill island to Pennsylvania, 
12, 32, 35, 20, 19, 20. 

From the south end of Windmill island to Jersey, 6, 
10, 14, 16, 16, 18, 18, 18, 10. 

From Kaign's Point to the piers at M'Leod's rope- 
walks, 8, 18, 24, 26, 24, 14— bar— 13, 19, 27, 28, 26,24, 
22, 17, 13, 10, 10. 

From Jersey to Pennsylvania, at a point about half 
way between Kaign's and Gloucester Points, 13, 22, 31, 
£8, 32, 21, 19, 17— bar— 17, 17, 19, 22, 24, 20, 16, 12. 

From the wharf at the Point to Jersey, 23, 25, 29, 33, 
27, 26, 25, 23, 14, 6, 4. 

From Gloucester wharf to Pennsylvania, 9, 14, 18, 24, 
26, 33, 38, 31, 25, 17, 5. 

From the north end of League island to the Windmill, 
Jersey, 3, 4, 7, 9, 10, 12, 12, 12, 13 — shoal called the 
Horse Shoe— 20, 29, 36, 30, 18, 15, 13, 9, 7, 5. 

From a white house on League island, commonly called 
Buttermilk Tavern, to a point two hundred yards below 
Eagle Point, 6, 11, 19, 22, 23, 26, 25, 24, 25, 26, 28, 29, 
29, 29, 28, 19, 10, 5, 4. 

From the south end of League island to Jersey, 1, 3, 7, 
12, 15, 19, 24, 24, 29, Z7 , 25, 24, 21, 18, 15, 10, 8, 1— 
bar — 4, 11, 21, 19. 

Across the mouth of Schuylkill, from east to west, 10,. 
15, 20, 28, 30, 23, 15, 10. 



35 

Schuylkill brings out over the flats from 8 to 10 feet. 

From Red Bank, near the Telegraph, towards the old 
Lazaretto, 10, 22, 12, 2— bar — 1, 1, 2, 4, 8, 13, 16, 17, 
18, 20, 26, 28, 29, 29, 28, 23, 22, 18, 10, 8, 6, 5, 4, 3, 3, 
5, 2. 

From the first pier below the fort, to Davis's pier, or 
fort Gaines, 23, 23, 26, 29, 30, 29, 31, 27, 24, 24. 

From fort Gaines to Jersey, 3, 4, 6, 9, 14, 14, 13, 11, 

10, 10, 14, 19, 20, 14, 7, 3, 1. 

From Boom or Diamond piers to Jersey, 42, 33, 30, 31, 
29, 25, 23, 16, 8, 5— bar— 4, 5, 4, 4, 14, 13, 12, 17, 19, 
20, 16, 10, 7, 0— bar— 0, 2, 1, 1. 

From a point near the middle of Hog island to Jersey, 
9, 18, 23, 28, 28, 26, 24, 17, 11, 8, 12, 14, 31, 29, 16, 14, 

11, 13, 12, 9, 9, 7, 6, 4, 3. 

From the south point of Hog island to Jersey, 6, 7, 8, 

12, 15, 15, 11, 11, 9, 6, 4— bar — 4, 14, 19, 24, 28, 33, 30, 
28, 27, 21, 23, 24, 24, 22. 

From the north point of Maiden island to Billingsport 
wharf, Jersey, 2, 6, 7, 9, 13, 23, 30, 34, 30, 28, 26, 23, 
22, 21, 18, 10. 

From the north point of Maiden island to Martin's bar, 

2, 8, 11, 13, 12, 15, 16, 7. 

From the north point of Tinnicum island to Pennsyl- 
^ vania, 1, 3, 7, 12, 12, 14, 12, 10, 9, 9, 9, 10, 11, 13, 12. 
From the north Point of Tinnicum island to Jersey, 9, 
18, 28, 29, 32, 37, 37, 40, 42, 41, 35, 18, 6. 

From the mouth of Clemell creek to Tinnicum island, 

3, 6, 10, 16, 18, 20, 29, 29, 30, 30, 29, 29, 21, 20, 15, 9. 
From the wharf at Thompson's Point to Tinnicum 

island, 5, 8, 14, 20, 20, 23, 26, 29, 29, 29, 30, 31, 31, 
28, 17. 

From the north end of Monnis's island to Jersey, 1, 2, 

4, 5, 4, 3. 

From the south end of Tinnicum inland to Jersey, 4, 
14, 20, 24, 28, 29, 28, 26, 26, 24, 22, 18, 19, 17, 9, 



36 

From the Lazaretto wharf to Tinnicum island, 20, 11, 
—a shoal— 16, 16, 14, 17, 18, 19, 20, 21, 22, 23, 19, 15, 
13, 8. 

From the south point of Tinnicum island to Pennsyl- 
vania, 11, 23, 26, 25, 25, 22, 19, 11. 

From the north end of Chester island to Jersey, 6, 15, 

20, 18, 9, 2. 

From the north end of Chester island to Pennsylvania, 
1, 4, 10, 19, 26, 30, 33, 18 — lower end of the bar from 
Tinnicum— 24, 26, 20, 10, 5. 

From the south point of Chester island to Jersey, 10, 
17, 20, 19, 15, IS, 10, 9, 6. 

From the north wharf at Chester to the south point of 
Chester island, 20, 21, 25, 27, 29, 31, 31, 31, 28, 25, 23, 

21, 19, 18, 15, 12, 4, 4, 3, 7, 10, 7, 8. 

From Pennsylvania to Jersey, half way between Ches- 
ter and Schiver's island, 8, 19, 23, 28, 29, 22, 17, 12, 13, 
16, 14, 8, 13, 13, 15, 17, 10, 4, 1. 

From the north point of Schiver's island to Jersey, 4, 
5, 6, 5, 4. 

From the north point of Schiver's island to Pennsylva- 
nia, 18, 20, 20, 20, 22, 23, 24, 26, 28, 30, 30, 27, 23, 20, 
15, 11. 

Across the bar, below fort Mifflin, there is, in the deep- 
est part of the channel, about 12 feet. The channel is 
narrow, and liable to many changes. 

The following are the soundings, taken at low vt^ater, 
on the 29th of July, 1820, four days after the full moon, 
at the end of all the principal wharves in Philadelphia, 
beginning at Kensington, and descending the river. 





feet. 




feeu 


1 Seguin's wharf. 


16 


5 Warder's wharf, 


19 


2 Saxton's do. 


16 


6 Walter's do. 


19 


3 Nagle's do. 


16 


7 Bubble's do. 


13 


4 Stiles's do. 


16 


8 Hains's do. 


6 



37 



feet. 

9 Randolph's wharf, 25 

10 Bi'ittoii's do. 26 

11 Callowhill St. do. 28 

12 Katz's do. 30 

13 West's do. 30 

14 Vine St. upper do. 19 

15 Flintham's do. do. 30 

16 Flintham's lower do. 12 

17 Smith's wharf, 36 

18 Race St. do. 42 

19 Warder's do. 37 

20 Pratt's do. 19 

21 Hodge's do. 22 

22 Smith's do. 20 

23 Sumerl's do. 25 

24 Arch St. wood do. 40 

25 Perot's wliarf, 20 

26 Girard's do. 42 

27 Fish Market do. 22 

28 Market St. do. low- 

er side, 20 

29 Chestnut St. wood 

wharf, 36 

30 Chestnut St. wharf, 

lower side, 12 

31 Gardner's wharf, 20 

32 Walnut St. upper and 

lower side, 6 

33 Ross's wharf, 20 

34 Morton's do. 18 
5,5 Morris's do. 20 

36 Hamilton's do. 20 

37 Drawbridge wood 

wharf, 26 

38 Wall's wharf, 22 



feet. 

39 Spruce St. do. 

R. Wain's, 19 

40 Sims's wharf, 31 

41 Pine St. wharf, 7 

42 Willing & Francis' 

upper wharf, 25 

43 Willing & Francis' 

lower wharf, 15 

44 Guthbert's wharf, 14 

45 Clapier's do. 15 

46 W. Wain's do. 32 

47 Penrose's do. 27 

48 Almond St. wood 

wharf, 20 

49 Ogleby's wharf, 18 

50 Huddle's do. 8 

51 Alberson's do. 14 

52 Catherine St. do. 20 

53 Queen St. do. up- 

per side, 18 

54 Queen St. do. low- 

er side, 12 

55 Christian St. wh. 17 
5Q Delevau's do. 15 

57 Ware's do. 15 

58 Berton's do. 15 

59 Humphreys' do. 14 

60 Prime St. do. 6 

61 Navy yard do. up- 

per side 14 

62 Navy yard do. 

lower side, 1 1 
The end of Smith's wharf, 
on the island, is at the 
low water mark. 



38 

The wharf, nearly oppo- above tlie low water 

site Pine St. on the mark. 

island, is 10 feet above The lower wharf, on the 

the low water mark. island, is 12 feet abore 

Humphreys' wharf, on the low water mark. 

the island, is 15 feet 

The wharves from Callowliill street to Chestnut street 
have the deepest water. This may be accounted for, from 
the circumstance, that the water, descending the channel 
east of Petty's island, spends its whole force against the 
wharves in that vicinity. Shortly after the water leaves 
Chestnut street wharf, it takes a direction over towards 
the south end of Windmill island, leaving the wharves in 
South wark considerably to the west of the bed of the river, 
and consequently in shoaler water. 



The bar, opposite Philadelphia, and at the north end 
of Windmill island, has undergone one of the greatest 
changes, during the last year, that was ever known. On 
the l6th of January last, a storm from the east broke up 
the icy fetters in the river. On the 17th, the wind blew 
strong from the southward j and the tide rose higher than 
it had done for a considerable time previous, inundated 
many of the wharves, and covered them with drifting ice. 
Shortly after tlie flood had set in, a large body of ice was 
collected on the bar, nearly opposite Arch street, to the 
height of nearly twenty feet, in the short period of about 
ten or fifteen minutes, and continued there a number of 
days. There can be no doubt that this bed of ice was 
instrumental, in connexion with the drifting ice, in pro- 
ducing the great change that followed. 

The wreck lying on the east side of the island, last 
year, was on a line with the soutli edge of the wharf; 
since which, it has been removed in a line with the north 



39 



^dge of the wharf. It is highly prohable that this change 
of position has promoted the change of the bar in that 
vicinity. 

The bar, a short time since, was surveyed, in order to 
ascertain the precise change that has taken place since 
last year. The draught in the Plate, at A, represents the 
state of the bar, on the 4th of October, 1819 j and at B, 
its state agreeably to the recent survey, taken on the £Oth 
of July, 1820. From the inspection of these, it will be 
obvious that the channel of last year is now converted into 
a bar, and the bars of last year into channels. 

On the ebb tide, particularly towards the close, the tide 
runs with considerable strength across the bar towards 
the Jersey shore. This was also found to be tlie case on 
the bar north of Davis's pier, opposite fort Mifflin. 



Description of the machine by which the rise and fall of 
the tide were ascertained. 



Let A be an upright post, to be 
driven firmly into the ground, in 
a suitable depth of water ^ 

B, the lower float board ; 

C, the upper float board ; 
n, the springs. 

As the tide rises, the float board 
C will also rise, and the springs 
n n continue to pass over the 
notches, until the water has at- 
tained its height j at w hich posi- 
tion the float board C will remain, 
being prevented from falling with 
the tide by the springs n n. 



B- 



B 



-^ 



^\ 






'av 



\0V 



40 

In like manner, the float board B will continue to de- 
scend until low water, where it will be retained Uy the 
springs nn on the top of it, and prevented from rising 
with the tide. 

A rod, as at D, duly marked, and passed through a 
hole from the upper float board, so as to rest nn the lower 
float board, will designate the height of the tide above 
low water. 

If this machine be left in the water, it will exhibit the 
highest and lowest tide during the year, or for any length 
of time. 



Description of the Plotting Table. 

This instrument is similar to the common draft board, 
both as regards its frame, and the plan of fixing the pa- 
per for drawing. It may be made either square or ob- 
long, and of any size, to suit the extent of the draught, 
and the degree of accuracy required. Round the frame, 
(Fig. 3) are graduated the degrees and quarters of a cir- 
cle whose centre is in the middle of the instrument. A 
strip of narrow paper may be glued round the frame, to 
receive the marks of the degrees and quarters. But strips 
of brass or box-wood, let into the frame, for the gradu- 
ated degrees, would be much more durable, though they 
are not so easily marked. This instrument may be made 
portable, by placing hinges on the two upper sides of the 
opposite corners, and on the inside of the remaining cor- 
ners of the frame ; and having the board for the paper 
composed of pieces. 

In proceeding with the application, the instrument will 
be sufficiently explained. 

To draw a line parallel to a given line. (Fig. 4.) Let 
tt 6 be a given line, to which it is required to draw an- 
other, parallel thereto. Lay tlie edge of the rule m on 



41 

the line a &, and at the same time press the piece n against 
the side B D. Move the rule m, and the piece n, in that 
position, and it will give the parallel direction for any line 
towards C and D. If the parallel he required towards A, 
let the piece n be placed against A C, while the edge of 
the rule m covers the line a h : then move the rule, as 
before, for the parallel position of any line towards A. 
Hence it is obvious, that the instrument will answer the 
purpose of an accurate parallel rule. 

To draw lines at right angles. (Fig. 5.) Press n against 
B D, and at the same time let the edge of the rule m cut 
90 on B D and A C. Draw one of the lines in that posi- 
tion, or in any other, by moving the rule as a b. Place 
n against C D, and at the same time let the edge of the 
rule cut on A B and C D. Draw the other line in that 
or any other position as c d, and it will be at right angles 
to the former line. 

To draw any angle. (Fig. 6.) Suppose 32 degrees be 
required. Place the rule in on A B and C D, and draw 
a line there, or in any parallel position, as a h. Let the 
rule m be placed at 32 in A B, and at 32 in C D, the 
edge of which will be 32 degrees, with the former line 
drawn from to 0, making the angular point in the cen- 
tre, from which the degrees are all drawn. If the angle 
is to be made in another place, as with the line a &, move 
the rule in that parallel position. If a 6 be near D, the 
piece n must be against C D ; but if a 6 be near the 
corner A, the piece n must be against A B, the reason of 
which is obvious. To draw any other angle, in any part 
of the table, will be readily understood from this example. 

From these three problems, it is evident that all the 
cases of trigonometry may be readily projected and re^ 
solved. 

-6 



42 

To plot a survey. (Fig. 3.) For example 

ch. lin ks. 



1. 


N. 50° E. 


9 


60 


2. 


S. 32° E. 


16 


38 


3. 


S. 41° W. 


6 


30 


4. 


West 


8 


43 


5. 


N. 79° W. 


10 


92 


6. 


N. 5° E. 


11 


25 


7. 


S. 83° E. 


6 


48 



It is scarcely necessary to say, that a line drawn from 
on A B to on C D, or any parallel to the same, will 
represent a meridian ; tliat a line from 90 on B D to 90 on 
A C, will represent the east and west line ; that the top 
represents the north, the bottom the south, the right the 
east, and the left the west. 

The point of the first station may be assumed anywhere 
on the paper, so that, on protracting the field, there may 
not be a side thrown beyond the paper, in some of the 
subsequent courses. Let A be the point from which the 
field is protracted. Let the edge of the rule m be placed 
on 50 near the corner B, and 50 near the corner C ; the 
piece n, at the same time, against the side A C Move 
the rule to the suitable position A, the assumed point, and 
draw the line A B, on which set off, from any scale of 
equal parts, 9.60. Place the edge of the rule m on 32 in 
A B, nearer the corner A, and 32 in C D nearer D. The 
piece w, at the same time against A B. Move the rule, 
until the edge thereof is in the point B ; and draw B C 
equal to 16.38. Let the edge of the rule be placed in 41 
near C, and 41 near B ; the piece n against C D. Bring 
the edge of the rule to the point C, and draw C D equal 
to 6.30. Again, let the edge of the rule be put on 90 in 
B D and A C, and the piece n either against A C or B D. 
Bring the edge of the rule to the point D, and draw D E 
equal to 8.43. In like manner proceed with the sides E F, 
F G, and G A. 



43 

To ascertain the contents of a survey. (Fig. 3.) For 
example, the field just protracted. The whole principle 
consists in throwing the figure into a triangle, which this 
instrument is capable of doing with great facility and 
accuracy. 

Assume any side for a hase line, which, when produced, 
shall not fall within any part of the figure, as A B neces- 
sarily would. Take B C, which produce indefinitely to- 
wards X and y. Lay the edge of the rule m on the point 
B and G, and the piece n against the side A C. Move 
the rule in that position to the point A; mark the point of 
intersection of the edge of the rule, and the base line B C 
in a. Place the edge of the rule in F and a, and move 
the rule in that position to the point G. Mark the point 
6, and place a circle round it for distinction, as the apex 
F is now arrived at a point whose distance is the greatest 
from the hase line. So also proceed to reduce the parallel 
position of the points C and E to D, and mark on the 
base line the point of intersection d; and, with the paral- 
lel position F and d!, reduce E to e. Tlien will the field 
be reduced to the triangle ¥ h e. The length of the base 
e b being ascertained by the compasses, and multiplied by 
half the perpendicular, will give the area. 

The demonstration of whicli is as follows. The triangle 
a A G is equal to the triangle A B «, being constituted 
on the same base A a, and between the parallel lines A a 
and G B. So also the triangle 6 F a is equal to the tri- 
angle G F a, being constituted on the same base F a, and 
between the parallel lines G 6 and F a. Therefore the 
triangle F 6 a is equal to the figure F G A B a F. In like 
manner may the triangle F e C be proved to be equal to the 
figure C D E F C And consequently the triangle 6 F e 
is equal to the whole figure A B C D E F G A. In as- 
suming a side for the base, it is best to take that side 
which would throw the survey in a triangle nearest the 
equilateral form. The base of this triangle was found to 



44 

be 26 chains 8 links ; and the perpendicular, 21 chains 35 
links ; from which the area was found to be 28 acres, 2 
roods, 1.744 perches ; — by calculation, 28 acres, 2 roods,, 
2 perches, differing about one-fourth of a perch. 

The size of the instrument by which the river was pro- 
jected, was nearly three feet square ; and so constructed 
as to admit the paper (which, when prepared for the map, 
was nearly thirteen feet long) to be drawn forward as the 
draughting progressed. 

On the utility and superiority of this invention, I deem 
it unnecessary to make any remarks. 



MY grateful acknowledgments are due to those gentle- 
men who kindly promoted the interest of the different 
experiments made on the river, and for the assistance 
which they so cheerfully afforded on that occasion. 

A report having been industriously circulated, last win- 
ter, that gross inaccuracies existed in the soundings of 
that part of my survey between Windmill island and the 
Jersey, and near the site of a certain contemplated bridge, 
I feel it a duty to myself and the public, to testify against 
such misrepresentations. To satisfy the public, to whom 
I am accountable for the faithful discharge of a public 
trust, I present for their perusal the following certificates, 
which first show that I was duly qualified for the work 
which I was called to perform ; and secondly, that I have 
been faithful, and am correct in that part of my survey 
which has been shamefully contradicted, by certain per- 
sons, excited by interested motives. 



David M'Clure, Esq. of this city, has shown to me a 
draught and description of his survey of the river Dela- 
ware. He has also explained the method used by him to 



45 

take the soundings, and to describe the shores, islands, 
flats, and bars in the river. All which appear to have 
been performed upon strict geometrical principles, in such 
way as ought to ensure accuracy in the work. 

Samuei. Hains, 

City Surveijor. 
Philad. Jaiu 8, 1820. 



I have also heard from Mr. M'Clure an explanation of 
the methods adopted in making the survey of the river 
Delaware, and concur with Mr. Hains in the opinion ex- 
pressed above. 

R. M. Pattersokt, 
Professor oj Mathematics in the Univ. of Penn. 



I also have examined Mr. M'Clure's draught ; and, 
although I do not profess to be versed in such matters, am 
inclined to think it has been executed with diligence and 
success, and may be rendered useful. 

Frederick Beasiey, 

Provost of the Univ. of Penn. 



The following is from Captain James Josiah, master 
warden, and Joseph S. Lewis, Esq. 

Philad. Feb. 15, 1820. 
Some doubts having been suggested, respecting the 
accuracy of Mr. M'Clure's survey of the river Delaware, 
the subscribers this day proceeded to sound the river, from 
"Windmill island towards Camden, on a line, as nearly 
as they could ascertain it, of the contemplated bridge. 



46 

The ice on the east end of the island was standing; and 
they took a boat, and passed over it, commencing sound- 
ing about one hundred feet from the east side of the island, 
and found, at about every hundred feet, the following 
soundings, — the tide being about an ordinary high water: 
8, 9, Hi, 15i, 17, 17i, 18, 17i, 17i, 17, 14i, 12, Hi, 12i, 
Hi. 

James Josiah, 
Joseph S. Lewis. 

The above soundings, being reduced to low water, by 
allowing the ordinary rise of five feet, will give six inches 
more than that exhibited in my chart. 



"We, the subscribers, do certify, that, on the 3d of Au- 
gust, 1820, we accompanied David M'Clure, Esq. on an 
examination of the channel between Windmill island and 
the Jersey, at low water ; that we had the satisfaction, on 
sounding the said channel, to compare the same with the 
original draught, which was before us ; and can declare, 
that we are fully of the conviction, that it is substantially 
correct, and corresponds to the low water mark at which 
it was taken. 

We found, throughout the whole channel, in its various 
parts, uniformly one foot more than is exhibited in Mr. 
M'Clure's chart, owing, as may be inferred, to the low 
water being one foot higher than it was at the time the 
soundings were taken for the chart. 

We found, throughout the channel, a deptli of thirteen 
feet, the narrowest part of which, as near as could be es- 
timated, was four hundred and fifty feet, commanding a 
a depth of eleven feet. 



47 

To prevent any mistakes, the line by which the sound- 
ings were taken, was carefully measured, before we com- 
menced the inspection. 

Francis Troubat, 
William G. Whyte, 
James West, 
William Tremper, 
William E. Tucker. 



Report of the Committeef on the subject of the Survey of 
the River Delaware. 

The Committee appointed by the Select and Common 
Councils, to have a survey of the river Delaware made, 
from Petty's island to one mile south of Chester, beg 
leave to report to Councils, that they proceeded in the 
execution of the trust (Committed to them, by employing 
Mr. David M'Clure as surveyor, and competent hands as 
assistants, who commenced the survey on the 26th day of 
June last, and finished the same on the 9th day of October 
last ; that the surveyor has made a Report, and a drauglit 
of the survey, which the Committee believe is entirely 
accurate, and which they herewith submit to Councils as 
part of their Report. All which is respectfully submitted- 

Joseph S. Lewis, 
J. W. Thompson, 
Stephen Girard, 
John M'Clintock. 

Fhiladelphia, February 10, 1820. 



INDEX. 

An account of the changes that have taken place in the river 

Delaware, - ..... 5 

Some remarks upon the inside channels, ... 6 
Some account of the bar below Fort Mifflin, and of Davis's Pier, 

or Fort Gaines, ....... 7 

Remarks on the manner in which sediment is collected, and 

shoal water produced, -8 

General observations on the current, - - - - - 8 

Remarks on the banks of Hog Island, - - ... 9 

An account of the channel east of Windmill island, - - 10 

The highest and lowest tides, when produced, - - - 12 

The rise and fall of the tide, for every half hour, - - - 12 

The effects of a freshet, - - - - - 14 

General remarks on the theory of the tides, - - - 14 

Tides supposed to ascend above their level, - - - 15 
The distance floating matter is carried down by the current, at 

the close of the ebb and flood, - - - - - 17 

Remarks on the fall of the tide, towards the close of the flood, 18 
An experiment to find whether the surface or bottom of the 

river has the greater velocity, - - - - - 19 
An experiment to find the different velocities, from the surface 

to the bottom, ...... 19 

Tables exhibiting the different rates of the current, for every 

half hour, with the different velocities, from top to bottom, 24 
A calculation for the quantity of upper water brought down the 

river every twelve hours, - ----- 27 

Remarks on the different velocities of the current, - - 27 

Different vertical sections of the river, . - ... 28 

Remarks on the changes of the river, . .... SO 

The soundings for the most remarkable places, - - - 33 

Depth of water at the end of the principal wharves at Philad. 36 

An account of the bar, opposite the city, - - - 38 

Description of the tide machine, ...... 39 

Description of the Plotting Table, - . . . . 40 

Certificates, - ..... 44 

Report of the Committee to Councils, - - - - 47 



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